1. Field of the Invention
The present invention pertains to providing mobility support for inter-networking. More particularly, the present invention relates to a method and system capable of providing mobility support for IPv4/IPv6 inter-networking based on a dual-stack architecture.
2. Description of Related Art
Advances in mobile and communication techniques make the rapid growth of the usage of mobile computers, so that the demand on mobility support of network protocols becomes intensive. Network protocol such as Internet Protocol (IP) is designed to provide packet addressing and routing functions. In order to support the mobility, some extensions on network protocols are proposed. However, there may be more than one network protocol existing, which makes the roaming in the networks with different network protocols difficult.
Mobile Internet Protocol (Mobile IP) provides mobility services for a moving node on the Internet. It aims to solve addressing and packet routing problems while the mobile station changes its point of attachment but still wants to communicate with other hosts by its original address. For a mobile station moved to a new network, the packets to the original address will not be routed to the new network since the new network has a different network prefix as its home network. To solve this problem, Mobile IP is proposed. Mobile IP version 4 (Mobile IPv4) is designed for Internet Protocol version 4 (IPv4). FIG. 6 schematically illustrates the inter-networking operation for the Mobile IPv4. In general, mobility agents advertise their presence by agent advertisement messages. A mobile node 91 receives these agent advertisements and determines whether it is on its home network 92 or a foreign network 93. When the mobile node 91 detects that it is located on its home network 91, it operates without mobility services. On the other hand, mobile node 91 obtains a care-of-address from a foreign agent 97 while it detects that it has moved to a foreign network 93. The mobile node 91 operating away from home then registers its new care-of-address with its home agent 94. Then data packets 95 sent to the mobile node's home address are intercepted by its home agent 94, tunneled by the home agent 94 to the mobile node's care-of-address, received at the tunnel endpoint. In the reverse direction, data packets sent by the mobile node 91 are generally delivered to their destination using standard Internet Protocol (IP) routing mechanisms.
As to Internet Protocol version 6 (IPv6), the next generation Internet Protocol, it has already taken mobility issues into consideration. Mobile IP version 6 (Mobile IPv6) further enhances mobility functions in IPv6. Mobile IPv6 shares many ideas in the Mobile IPv4 and inherits some new features in IPv6. With reference to FIG. 7, the basic operations of Mobile IPv6 are illustrated. With Mobile IPv6, a mobile node 91 is always addressable by its home address, and packets 95 addressed to its home address are routed to it using conventional Internet routing mechanisms. While away from home, a mobile node 91 detects of such by receiving a router advertisement form an IPv6 router 96. The mobile node 91 registers one of its care-of addresses with the router 96 on its home link, and requests this router 96 to function as the “home agent” for the mobile node 91. The mobile node's home agent 94 thereafter uses proxy neighbor discovery to intercept any IPv6 packets 95 addressed to the mobile node's home address on the home link, and tunnels each intercepted packet to the mobile node's primary care-of-address. The binding update and binding acknowledgement destination options, together with a “Binding Request” destination option, are used to allow IPv6 nodes communicating with a mobile node, to dynamically learn and cache the mobile node's binding. When a mobile node 91 sends a packet while away from home, it sets the source address in the packet's IPv6 header to one of its current care-of addresses, and includes a “Home Address” destination option in the packet, giving the mobile node's home address.
The transition of two different addressing protocols such as IPv4 to IPv6 is a very important issue. Several transition techniques are proposed to transmit IPv4 packets in an IPv6 network or vice versa. However, the transition problems involving in Mobile IP are almost ignored, so that it is difficult to support the mobility in heterogeneous networks. For example, concerning a situation that a mobile IPv4 node moves to an IPv6 network, since IPv6 eliminates the concept of foreign agents, the node can not receive the agent advertisement message and fails to register its care-of-address to the home again. On the other hand, concerning the situation for a mobile node with IPv6 address migrating to an IPv4 network, the node can not receive IPv6 router advertisement, and also fails in the care-of-address registration.
Therefore, it is desirable to provide an improved method and system for providing inter-networking mobility support, so as to mitigate and/or obviate the aforementioned problems.